1. Field of the Invention
This invention relates generally to a receiver having a preset tuner and, more particularly, to a receiver which can automatically preset reception channels by searching for both terrestrial wave television broadcast channels and CATV broadcast channels according to their channel plans.
2. Description of the Prior Art
To conduct preset on a receiver of this kind capable of receiving both television broadcasts and CATV broadcasts, a user is required to decide if a terminal on the wall is for reception of television broadcasts or CATV broadcasts. According to such decision, the user then has to switch the receiver to a television broadcast or CATV broadcast side so that preset can be implemented. In this manner, the conventional receiver has been troublesome upon presetting and hence inconvenient for the user.
Accordingly, the present applicant has proposed an improved receiver of this kind in Japanese Patent Laid-open No. H7-87415 [H04N5/44, 7/16] laid open on Mar. 31, 1995. This art has solved a drawback to the need of manually switching the receiver and made it possible to automatically perform presetting for both television and CATV broadcast channels.
According to the proposed prior art, when reception is over a plurality of channels of a frequency band assigned only for CATV broadcast, preset must be conducted by automatically performing channel search according to a CATV broadcast channel plan. When reception is over one or less channel in a CATV frequency band, preset must be by automatically performing channel search according to a channel plan assigned for television broadcast.
The prior art described in Japanese Patent Laid-open No. 7-87415 provides automatic determination for receiving television broadcasts or CATV broadcasts. Suitable channel preset can be made in an automatic way without requiring user""s decision or switching over on the receiver. Thus, this art is improved in usability excepting for a problem to be resolved. In the prior art, however, there is a possibility that a CATV broadcast even not to be received be determined as a CATV broadcast in an adjacent one of successive channels. This possibly result in erroneous setting as a television broadcast.
It is therefore a primary object of the present invention to provide a receiver capable of positively presetting CATV broadcast channels as well as television broadcast channels.
Another object of the invention is to provide a receiver capable of performing such preset in a brief time.
A receiver having a preset tuner according to the present invention is a receiver, having preset tuner for searching for channels of at least one of television broadcast and CATV broadcast and presetting data over a receivable channel onto a memory, comprising: a determination means for determining whether broadcast signals have been received over two or more of successive channels; and a preset means for presetting a reception channel according to a channel plan of at least one of television broadcast and CATV broadcast depending upon a result of determination by the determination means.
In one embodiment, the determination means includes a counter, an increment means for incrementing the counter when a reception signal is obtained over a set channel, a decrement means for decrementing the counter when no reception signal is obtained over the set channel, a count value determination means for determining whether a count value of the counter is a predetermined value or not.
The determination means includes a reception determination means for determining whether a reception signal is to be obtained over the set channel or not. The reception determination means includes a synchronization signal detecting means.
In television broadcasts, the channels in an adjacent relation are not utilized because of small P/S ratio. Accordingly, in actual frequency assignment, broadcast stations are not assigned to the channels in an adjacent relation but to the channels by skipping one channel or more without exception. Meanwhile, in CATV broadcast, the P/S ratio is taken great because of the necessity of packing many stations within a limited band range. Thus, in the CATV broadcast, broadcast stations are dotted throughout. The present invention has been made by considering on such a fact.
For example, a synchronizing signal is detected by a synchronizing signal detection circuit, a reception determining means at that time detects that a broadcast signal has been obtained over a set channel, for example, by a microcomputer. An increment means, in turn, increments a counter. However, if no broadcast signal exists over the set channel, the counter is decremented by a decrement means.
Consequently, where the microcomputer sets channels in an adjacent relation in order, if broadcast signals are detected over two or more successive (adjacent) channels, a number of xe2x80x9c2xe2x80x9d or greater is counted on the counter. In this case, the CATV channels are preset according to a CATV broadcast channel plan.
In television broadcast there is no case of practically using the channels in an adjacent relation because of small xe2x80x9cPicturexe2x80x9d/xe2x80x9cSoundxe2x80x9d (xe2x80x9cP/Sxe2x80x9d). Consequently, the counter will not count a value of equal to or greater than xe2x80x9c2xe2x80x9d. In this case, the preset means presets channels according to a television broadcast channel plan.
According to the invention, there is no necessity for a user to switch between television broadcast and CATV broadcast, similarly to the aforesaid reception technology, thus improving usability. Furthermore, in the invention, where a reception signal is successively detected over the adjacent channels, preset can be positively made for CATV broadcast.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.